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Biomedical subjects

R C Johnson

Publications and source records attributed to R C Johnson.

At least 271 records · Page 15Linked to original sources
PubMed1988

Role of immunoglobulin G in killing of Borrelia burgdorferi by the classical complement pathway.

The antibody and complement requirements for killing of Borrelia burgdorferi 297 by normal human serum (NHS) and NHS plus immunoglobulin G (IgG) were examined. B. burgdorferi activated both the alternative and classical complement pathways in NHS. In NHS chelated with 10 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid plus 4 mM MgCl2 (Mg-EGTA) to block classical pathway activation, consumption (activation) of total hemolytic complement, complement component 3 (C3), and C9 by B. burgdorferi was observed. Furthermore, challenge of unchelated NHS with 297 cells resulted in the consumption of C4, in addition to an increase in C3 and C9 consumption over that observed in chelated serum. In spite of complement activation, B. burgdorferi was resistant to the nonspecific bactericidal activity of NHS. The addition of human anti-B. burgdorferi IgG to NHS, however, resulted in the complete killing of 297 cells. Bactericidal activity of this serum was abrogated if NHS was immunochemically depleted of C1, indicating that killing was mediated by the classical pathway. The manifestation of bactericidal activity was accompanied by a large increase in total complement and C3 consumption over that observed in NHS alone. Under similar conditions, only a minimal increase in C9 consumption was observed. No increase in total complement consumption was observed if NHS plus anti-B. burgdorferi IgG was treated with Mg-EGTA prior to challenge. The results of these experiments demonstrate that B. burgdorferi is resistant to the nonspecific bactericidal activity of NHS, in spite of classical and alternative complement pathway activation. B. burgdorferi is sensitive to serum, however, in the presence of IgG, which mediates bacterial killing through the classical complement pathway.

Antibodies, Bacterial↗
PubMed1988

Characterization of a circular plasmid from Borrelia burgdorferi, etiologic agent of Lyme disease.

Borrelia burgdorferi, the etiologic agent of Lyme disease, was recently shown to contain plasmid DNA. Two plasmid species have been described in strain CT1, a Wisconsin tick isolate: a 9.2-kilobase entity; and a larger, 70-kilobase entity. Characterization of the 9.2-kilobase entity by using DNase I and restriction endonucleases demonstrated that the plasmid is supercoiled and exists as a stable dimer in this strain. The role played by the plasmid in B. burgdorferi is unknown.

Borrelia↗
PubMed1988

Familial transmission of alcohol consumption and the flushing response to alcohol in three Oriental groups.

Multivariate path analysis was used to examine the etiologies of variation and covariation of flushing after alcohol use in nuclear families of Korean, Taiwanese, Japanese and Caucasian ancestries. Phenotypic variances and covariances were partitioned into familial (additive genetic and common family environment) and environmental components. Although alcohol consumption and flushing varied greatly among the different groups, familialities, estimated from components of mother, father and at least one child, were remarkably similar. The familialities for flushing were 0.48 for Japanese, 0.56 for Koreans and 0.35 for Taiwanese; flushing is infrequent in Caucasians and thus was not analyzed. Familialities were lower for consumption, but like flushing, were consistent across ethnic groups (Japanese, 0.27; Koreans, 0.24; Taiwanese, 0.15; Caucasians, 0.28). The genetic correlation between flushing and alcohol consumption was high. Thus, to the extent that flushing influences alcohol consumption, the covariance is most likely genetic.

Adolescent↗
PubMed1988

Pulmonary artery disruption from blunt thoracic trauma.

Blunt chest trauma occurs in up to 50 per cent of all fatal motor vehicle accidents and is the primary cause of death in 12-25 per cent; yet only 15 per cent of patients with chest trauma arriving alive to the emergency department require early thoracotomy. Pulmonary artery disruption from blunt trauma is extremely rare. Two patients both women, older and obese with multiple rib fractures and little pulmonary parenchymal damage are reported. Neither had injury to the aorta, heart or intra-abdominal organs. One patient survived after lateral repair of the left main pulmonary artery and the other exsanguinated from a laceration of the right main pulmonary artery. Intrapericardial exposure of the proximal pulmonary arteries may be necessary for control of hemorrhage. Trauma surgeons should be familiar with this technique. Indications for immediate thoracotomy should include: massive hemothorax (greater than 1000 ml), continued bleeding greater than 300 ml in the first hour, bleeding greater than 200 ml/hr for 5 hours, or increasing hemothorax in spite of tube thoracostomy. Close adherence to these guidelines would have allowed both patients to be explored earlier.

Accidents, Traffic↗
PubMed1988

Acute pelvic limb paralysis induced by a lumbar fibrocartilaginous embolism in a sow.

A diagnosis of fibrocartilaginous embolism was made in a mature mixed-breed sow with a history of an acute onset of pelvic limb paralysis. Within a single section of lumbar spinal cord, there was severe focally-extensive infarction of the right ventral gray horn. Within affected white matter, there was dilatation of multiple myelin sheaths with concurrent axonal swelling. A smaller focus of infarction was present on the contralateral side. Arteries at the periphery of both lesions contained a blue-gray material with staining characteristics similar to that evidenced by the nucleus pulposus present within intervertebral discs. Grossly, no abnormalities were present within the vertebral column.

Acute Disease↗
PubMed1987

Subnormal concentrations of serum selenium and plasma carnitine in chronically tube-fed patients.

Forty-seven tube-fed nursing home patients were investigated with regard to serum or plasma selenium (Se), carnitine, and red blood cell (RBC) glutathione peroxidase (GSH-Px). Thirty-six patients were tube fed with Isocal, and 11 were tube fed with Compleat B, an L-carnitine-containing formula. Eighteen elderly nursing home patients and 10 young adults served as controls. Serum Se and plasma carnitine were lowest (p less than 0.05) in the Isocal patients. In all 36 Isocal subjects, Se was below normal, and in 26% of Isocal patients RBC GSH-Px was also below normal. Free and total carnitine were below normal in most Isocal subjects. All 11 Compleat B patients had subnormal serum Se, but most had normal carnitine concentrations. These data suggest that enteral formulae in nursing homes should contain greater than 100 micrograms Se and on the order of a mmol carnitine/1600 kcal.

Adult↗
PubMed1987

Cross-reactivity in serological tests for Lyme disease and other spirochetal infections.

Serum specimens from 163 persons with Lyme disease, tick-borne or louse-borne relapsing fever, yaws, syphilis, leptospirosis, or Rocky Mountain spotted fever were analyzed to assess the specificity of indirect fluorescent antibody (IFA) tests, an enzyme-linked immunosorbent assay (ELISA), and microscopic agglutination (MA) procedures. Strong cross-reactivity occurred when sera from individuals with Lyme disease, tick-borne relapsing fever, and louse-borne relapsing fever were tested against heterologous Borrelia antigens. Antibodies to Borrelia burgdorferi bound to Treponema pallidum in immunofluorescence tests for syphilis. Sera from subjects with syphilis cross-reacted in IFA tests and the ELISA for Lyme disease. Immunoglobulin antibodies to Borrelia or Treponema spirochetes, however, did not react with serovars of Leptospira interrogans in MA or IFA tests, and the prevalence of false-positive results in the reciprocal analyses was negligible.

Antibodies, Bacterial↗
PubMed1987

Blunt trauma to the abdominal aorta.

This review of blunt trauma to the abdominal aorta is based on one case summary and 32 cases from the literature. Motor vehicle accidents caused about half of the reported cases. In 69% of the cases the diagnosis was made in the immediate or early period. Associated injuries were present in 71% of the cases. Most injuries occurred at the inferior mesenteric artery (33%) or the renal arteries (24%). Overall mortality was 27%. Lower extremity ischemia evident on physical examination may suggest the diagnosis. When blunt abdominal aortic injury is suspected without distal ischemia, aortography may be used to define or exclude the injury and further therapy. Only minimal intimal disruptions should be managed nonoperatively.

Adolescent↗
PubMed1987

Fis binding to the recombinational enhancer of the Hin DNA inversion system.

The recombinational enhancer of the Hin inversion system in Salmonella stimulates recombination in vitro 150-fold in the presence of the Escherichia coli host factor Fis. To gain an understanding of the roles of the enhancer and Fis in stimulating the Hin-mediated inversion reaction, we have used nuclease and chemical protection/interference studies and gel retardation assays to examine the interactions between Fis and the recombinational enhancer. These studies combined with mutational analysis defined the enhancer sequences required for Fis binding and function. Fis binds with different affinities to two domains within the enhancer sequence. The binding of Fis at each domain is independent of the occupancy of the other domain and appears to be to opposite faces of the DNA helix. These results support a model for the role of the recombinational enhancer in Hin-mediated inversion in which the interaction between Hin bound at recombination sites and Fis bound to each domain of the recombinational enhancer results in a structure with the proper alignment and topology to promote DNA inversion.

Base Sequence↗
PubMed1987

Leaf photosynthesis and conductance of selected triticum species at different water potentials.

Leaf gas exchange characteristics of a desert annual (Triticum kotschyi [Boiss.] Bowden) and the wheat cultivar TAM W-101 (Triticum aestivum L. em Thell) were compared over a range of leaf water potentials from -0.50 to -2.9 megapascals. At an ambient [CO(2)] of 330 microliters per liter, T. kotschyi had higher conductance and CO(2) assimilation (A) at a given water potential than T. aestivum. Under well watered conditions, A versus internal CO(2) concentration (C(i)) response curves for both species were similar in shape and magnitude, and the higher A of T. kotschyi at an ambient [CO(2)] of 330 microliters per liter was mostly related to the higher stomatal conductance of T. kotschyi. The higher conductance of T. kotschyi than T. aestivum under well watered conditions was associated with higher C(i) and lower water use efficiency. Under water deficits, however, C(i) at 330 microliters per liter ambient [CO(2)] did not differ significantly between species. T. kotschyi had higher A under water deficits than T. aestivum primarily because its A versus C(i) response curves had higher A at C(i) values above about 150 microliters per liter. The results show that conductance played an important role in the high A of T. kotschyi under well watered conditions, but under water deficits the high A of T. kotschyi was related more to the maintenance of a higher capacity for mesophyll photosynthesis.

Journal Article↗
PubMed1987

In vitro and in vivo susceptibility of the Lyme disease spirochete, Borrelia burgdorferi, to four antimicrobial agents.

The antimicrobial susceptibility of Borrelia burgdorferi isolated from human spinal fluid was determined in vitro and in vivo. A broth dilution technique was used to determine the MBCs of four antimicrobial agents. The Lyme disease spirochete was most susceptible to ceftriaxone (MBC, 0.04 microgram/ml) and erythromycin (MBC, 0.05 microgram/ml), then tetracycline (MBC, 0.8 microgram/ml), and finally penicillin G (MBC, 6.4 micrograms/ml). Syrian hamsters were used to determine the 50% curative doses (CD50s) of the four antimicrobial agents. Ceftriaxone and tetracycline had the highest activities, with CD50s of 24.0 and 28.7 mg/kg [corrected], respectively. Both erythromycin and penicillin G possessed low activities. The CD50 of erythromycin was 235.3 mg/kg [corrected], and the CD50 of penicillin G was greater than 197.5 mg/kg [corrected].

Animals↗
PubMed1987

Prevalence of Borrelia burgdorferi and Babesia microti in mice on islands inhabited by white-tailed deer.

Borrelia burgdorferi and Babesia microti were isolated from 35 of 51 white-footed mice (Peromyscus leucopus) and meadow voles (Microtus pennsylvanicus) captured on two Narragansett Bay, R.I., islands inhabited by deer, the principal host for the adult stages of the vector tick, Ixodes dammini. Immature ticks parasitized mice from both islands. From 105 mice captured on four other islands not inhabited by deer neither pathogen was isolated, nor were I. dammini found.

Animals↗
PubMed1987

Colony formation and morphology in Borrelia burgdorferi.

Two strains of Borrelia burgdorferi, B31 and 297, formed colonies when plated onto Barbour-Stoenner-Kelly medium solidified with agarose (1.3%) and incubated in a candle jar at 34 degrees C. Colonies differing in morphology were observed in both strains after 2 to 3 weeks of incubation. Strain B31 colonies were either compact, round (mean diameter, 0.43 mm), and restricted to the surface of the agarose medium or diffuse (mean diameter, 1.80 mm) and penetrating into the solid medium. Strain 297 colonies (mean diameter, 1.43 mm) either showed a raised center surrounded by a diffuse ring of spirochetes or consisted of numerous small spirochetal aggregates. Both colony types expanded into the agarose medium. Scanning electron and light microscopy confirmed that the colonies were formed by spirochetes. Twisted tangles of intertwined spirochetes were visible on the surface, with numerous spherical bodies among them, especially in the central regions. At the periphery, the borreliae were more loosely packed, and individual coils were discernible.

Animals↗